Coronary vessels, partially occluded by plaque, may become totally occluded by a thrombus or blood clot causing myocardial infarction, angina and other conditions. A number of medical procedures have been developed to allow for the removal of plaque from vessel walls or to clear a channel through the thrombus or clot to restore blood flow and minimize the risk of myocardial infarction. Carotid, renal, peripheral, and other blood vessels can also be blocked and require treatment. For example, atherectomy or thrombectomy devices can be used to remove atheroma or thrombus. Alternatively, in percutaneous transluminal coronary angioplasty (PTCA), a guide wire and guide catheter are inserted into the femoral artery of a patient near the groin, advanced through the artery, over the aorta, and into a coronary artery. An inflatable balloon is then advanced into the coronary artery, across a stenosis or blockage, and the balloon inflated to dilate the blockage and open a flow channel through the partially blocked vessel region. One or more stents may also be placed across the dilated region or regions. While some stenoses remain in place once dilated and/or stented, others are more brittle, and may partially crack and fragment after the dilation or stent placement, allowing the fragments to flow downstream where they may block more distal and smaller coronary vessels, possibly causing myocardial infarction, from that site. Consequences of embolization include stroke, diminished renal function, and impairment of peripheral circulation possibly leading to pain and amputation.
Saphenous vein grafts are often used to bypass occluded coronary vessels in coronary artery bypass surgery. With time, the grafts can become occluded with grumous. The grumous can also be dilated with balloons or removed in other ways. The grumous can present an even more difficult material to remove than thrombus, as the material is very friable, and likely to break into smaller fragments during the removal procedure.
Distal embolic protection devices have been developed to prevent the downstream travel of materials such as thrombi, grumous, emboli, and plaque fragments. Devices include occlusive devices and filters. Occlusive devices, for example distal inflatable balloon devices, can totally block fluid flow through the vessel. The material trapped by the inflatable devices can remain in place until removed using a method such as aspiration. However, aspiration cannot remove large particles because they won't fit through the aspiration lumen. Also, aspiration is a weak acting force and won't remove a particle unless the tip of the aspirating catheter is very close to the particle to be removed. During the occlusion, the lack of fluid flow can be deleterious. In coronary applications, the lack of perfusing blood flow can cause angina. In carotids, seizure can result from transient blockage of blood flow. In both coronaries and carotids it is not possible to predict who will suffer from angina or seizure due to vessel occlusion. If a procedure is started with an occlusive device, it may be necessary to remove it and start over with a filter device.
Some distal embolic protection devices include filters. Filters can allow perfusing blood flow during the emboli capture process. The filters can be advanced downstream of a site to be treated and expanded to increase the filter area. Emboli, such as grumous or atheroma fragments, can be captured in the filter until the procedure is complete or the filter is occluded. When the capacity of the filter is reached, the filter may then be retracted and replaced.
Distal embolic protection devices can be delivered over guide wires and within guide catheters. The distal embolic protection methods are normally practiced ancillary to another medical procedure, for example PTCA with stenting or atherectomy. The distal embolic protection procedure typically protects downstream regions from emboli resulting from practicing the therapeutic interventional procedure. In the example of PTCA, the treating physician must advance a guide wire over the aorta and into a coronary ostium. Advancing the guide wire through tortuous vessels from a femoral artery approach can be difficult, and vary with both the patient and the vessel site to be treated. Guide wires are typically selected by the treating physician, based on facts specific to the patient and therapeutic situation, and also on the training, experiences, and preferences of the physician. In particular, a physician may have become very efficient in using a specific guide wire to identify the left coronary ostium and then advance a balloon catheter over the positioned guide wire. The efficacy of the procedure may depend on the physician being able to use their favored guide wire.
The distal embolic protection device is preferably delivered using the same, favored guide wire. The phrases “distal embolic protection device” or “embolic protection device” are used herein to refer to embolic protection devices that are occlusive and/or filtering. The terms “distal embolic protection device” and “embolic protection device” are used interchangeably, as either may be used to protect a target site located either proximal to or distal to another treatment site. The term “embolic protection element” may be used generally to include both occlusive and filtering elements disposed near the distal region of a distal protection device shaft.
In the example PTCA procedure, a guide catheter extends proximally from the patient's groin area, and may be about 100 centimeters long, later having a 140 centimeter long guide wire proximal region extending from the guide catheter. The distal embolic protection device delivery catheter, nominally about 130 centimeters in length, can be advanced over the guide wire and within the guide catheter, until a short length of guide wire extends from both the guide catheter and delivery catheter. The guide wire can then be retracted and removed from the patient. In some methods, the distal protection device is then advanced through and out of the positioned delivery catheter, to the target site to be protected or filtered. In other methods, delivery is accomplished by disposing the distal embolic protection filter device within the delivery catheter distal region, and advancing the delivery catheter and embolic protection device together over the guide wire, and deploying the filter by retracting the delivery catheter while maintaining the position of the filter, thus forcing the filter distally out of the delivery catheter.
Advancement of the delivery catheter over a single length, nominally 130 centimeter long guide wire presents a problem. The treating physician can only advance the filter delivery catheter about 20 centimeters over the guide wire until the delivery catheter advances into the patient and the guide wire is inaccessible within the delivery catheter. The guide wire position should be controlled at all times so as to not be dislodged by the advancing delivery catheter from the hard acquired guide wire position within the patient.
One solution to this problem is to use a guide wire at least double the length of the delivery catheter. A 320 or 340 centimeter long guide wire can extend at least about 120 centimeters from the patient's groin, having an accessible region exposed at all phases of delivery catheter placement. However, the added length makes manipulating and rotating the guide wire very difficult for the treating physician. The extra length of the guide wire can be held by additional personnel to prevent the added wire length from falling to the floor, where it would become contaminated. However, not all cardiac catheter laboratories have personnel available to maintain control of the long guide wire. In many labs, the physician is working alone in the sterile field. Advancing a distal embolic protection device delivery catheter over a positioned, favored guide wire would be inherently more efficacious than requiring use of an unfamiliar, disfavored, or double length guide wire to position the delivery catheter.
With the distal filter in place, removal of the delivery catheter over the wire shaft of the distal filter device is ultimately desirable. If a single length, nominally 140 centimeter long, distal filter device shaft is extending about 20 centimeters proximally from the delivery catheter, a problem is presented. Once the delivery catheter is retracted about 20 centimeters, the proximal end of the wire would disappear into the proximal end of the retracting delivery catheter, and control of the distal filter device wire position lost. If the delivery catheter were further retracted, the retraction of the delivery catheter over the wire shaft may pull the distal filter device from its position. Again, a distal protection device having a double length wire shaft can be used. The double length wire shaft allows the delivery catheter to be retracted over the distal filter device shaft while presenting an exposed portion of the wire shaft at all times. As discussed with respect to the double length guide wire, the added length presents problems.
What would be desirable are distal embolic protection device delivery catheters that can be delivered over the single length guide wire favored by the treating physician and retracted over single length wire shafts of distal embolic devices.